It is conceived that the pigmentation such as speckles and freckles on the skin is caused when melanin is generated excessively due to hormonal disorders, the ultraviolet ray, or skin local inflammation and it deposits in the skin. The melanin, which causes skin pigmentation, is produced in melanocytes present in the epidermal basal layer. The melanin is produced when tyrosine is converted to dopaquinone by the action of an enzyme tyrosinase, subsequently further oxidized, polymerized, and changed to dark melanin.
Conventionally, it has been demanded to alleviate such skin pigmentation and realize a transparent white skin, which is so-called whitening of the skin. Alkoxysalicylic acid or a salt thereof is known as an active ingredient having good whitening effect for alleviating and preventing the abnormal deposit of melanin in the skin. However, generally, when alkoxysalicylic acid or a salt thereof is added to a water-in-oil-type emulsion composition, the stability over time is poor, sometimes posing a problem of causing phase separation between the oil phase and aqueous phase.
To improve the stability over time, a method in which the amount of a lipophilic emulsifier is increased, a method in which a wax is added to an external phase (oil phase), or the like, is used; however, these methods sometimes deteriorate a feel of use with respect to the spreadness and stickiness of a cosmetic. Thus, to improve these problems of the stability and the feel of use, it has been proposed that salts as a buffer and polyethylene glycol having a weight average molecular weight of 1,000 to 200,000 are added in predetermined amounts to a water-in-oil-type skin external emulsion containing alkoxysalicylic acid or a salt thereof (Patent Document 1).
On the other hand, an organic modified clay mineral such as Bentone is commonly added to a water-in-oil-type emulsion composition, not only to a water-in-oil-type emulsion composition containing alkoxysalicylic acid or a salt thereof, as a viscosity adjustor or emulsion stabilizer and also for the purpose of imparting a moist feel when used. Actually, the above Patent Document 1 also discloses production examples containing alkoxysalicylic acid or a salt thereof and an organic modified clay mineral (Examples 8 to 10).